Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a first image in a sequence of a display screen or portion thereof with a graphical user interface, showing the new design;

FIG. 2 is a front view of a second image thereof, shown without the broken line environment for clarity of disclosure; and,

FIG. 3 is a front view of a third image thereof.

The appearance of the animated image sequentially transitions between the images shown in FIGS. 1 through 3. The process or period in which one image transitions to another forms no part of the claimed design.

The outermost broken lines in FIG. 1 illustrate the environment of the design and form no part of the claim. The remaining broken lines, including all text, illustrate portions-of the display screen or portions of the graphical user interface that form no part of the claimed design.

The dash-dot and dash-dot-dot broken lines illustrate the boundaries of the design. The gray-shaded region between the boundary lines forms no part of the claimed design. The region enclosed by the dash-dot-dot boundary lines form part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface, as shown and described. 